Dermatitis Herpetiformis

Intense itching. A burning sensation. Clusters of small blisters that persistently break out on the elbows, knees, buttocks, back, or scalp. These symptoms are the hallmarks of dermatitis herpetiformis (DH), a skin manifestation of celiac disease. DH affects 15 to 25 percent of people with celiac disease, and these people typically have no digestive symptoms of the disease.

One such person is Rory Jones. Although plagued with celiac-related ailments including joint pain, thyroid disease, and early-onset osteoporosis, she never experienced intestinal symptoms and had no idea she had celiac disease. Then came the increasingly frequent appearance of itchy sores on her hands, which eventually spread to her face and arms. “The itching would wake me up at night,” said Jones, who sometimes bled from scratching in her sleep. “I wanted to scratch my bones.”

Dermatologists, allergists, and other specialists couldn’t determine the cause of her skin outbreaks and other symptoms. Another 4 years passed before she was diagnosed with DH and celiac disease.

Celiac and the Skin

How does a disorder that damages the intestines show up on the skin? When a person with celiac disease consumes gluten, the mucosal immune system in the intestine responds by producing a type of antibody called immunoglobulin A (IgA), explains John Zone, M.D., chairman of the Department of Dermatology at the University of Utah School of Medicine. As IgA enters the bloodstream, it can collect in small blood vessels under the skin, triggering further immune reactions that result in the blistering rash of DH.

Telltale Signs

The first clue that a skin eruption may be DH is that “it itches like crazy,” said Zone. “People are digging at themselves.” As a result, the blisters are almost always broken open by the time a DH sufferer seeks medical help.

The second characteristic sign of DH is its location on the body. Lesions most often appear on the extensor surfaces—the forearms near the elbows, the knees, and the buttocks. The outbreak of lesions also tends to be bilateral, meaning it appears on both sides of the body.

The grouping of the lesions provides a final clue. Although DH is not caused by the herpes virus, its lesions resemble those of herpes, hence the word “herpetiformis.” In both conditions, lesions form in small groups.

Still, DH is often confused with eczema, a common inflammatory skin disorder that, like DH, results in an itchy rash that is often scratched raw.

A Selective Disorder

DH can affect people of all ages but most often appears for the first time between the ages of 30 and 40. People of northern European descent are more likely than those of African or Asian heritage to develop DH. The condition is somewhat more common in men than women. And men are more likely to have atypical oral or genital lesions.

The unusual outbreaks of DH on Rory Jones’ forehead and eyelids may have led her dermatologists down the wrong path.

Diagnosing DH

For Jones, the diagnosis of DH came about in an unexpected way. An endocrinologist became suspicious of the unusual severity and early onset of her osteoporosis. In an effort to find a cause, her doctor sent a blood sample to Peter Green, M.D., director of the Celiac Disease Center at Columbia University, who was conducting a random screening for celiac disease in osteoporosis patients. Jones tested positive for the presence of antibodies that often indicate the presence of celiac disease and was scheduled to undergo an endoscopy to confirm the diagnosis. “At the hospital, while Dr. Green explained the procedure, he saw me scratching my hands and face,” said Jones. Green suggested she have a skin biopsy for DH. The endoscopy results were inconclusive but the skin biopsy was not. She had DH—and an answer to the source of her bone, joint, and thyroid problems.

A skin biopsy is the key tool in confirming a diagnosis of DH. Doctors take a skin sample from the area next to a lesion and, using a fluorescent dye that highlights antibodies, look for the presence of IgA deposits. Skin biopsies of people with DH are almost always positive for IgA.

Blood tests for other antibodies commonly found in people with celiac disease—antiendomysial and anti-tissue transglutaminase antibodies—supplement the diagnostic process. If the antibody tests are positive and the skin biopsy has the typical findings of DH, patients do not need an intestinal biopsy to confirm the diagnosis of celiac disease.

Treatment

The rashes caused by DH can be controlled with antibiotics such as dapsone. “What’s most interesting about DH is that the rash itself responds dramatically to dapsone, usually in 48 to 72 hours,” said Zone. This dramatic response—another hallmark of the disease—was once the basis for diagnosis, before skin biopsies became the norm. People who can’t tolerate dapsone may be given sulfapyridine or sulfamethoxypyridazine instead, although these drugs are less effective.

A strict gluten-free diet is the only treatment for the underlying celiac disease. Even with a gluten-free diet, dapsone or sulfapyridine therapy may need to be continued for 1–2 years to prevent further DH outbreaks. For people like Jones, who elected not to use dapsone, relief comes gradually as the diet does its job.

Jones’ circuitous path to a diagnosis is a common one for people with celiac disease. According to Zone, more than 95 percent of DH cases are misdiagnosed as eczema. Thankfully, once diagnosed, relief for most people with DH will come through treatment and strict adherence to a gluten-free diet.

September 2014

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